It's basically impossible to watch those with a dry eye, but that's not the film psychologists use when they need a tearjerker. In thousands of studies, researchers rely on the final scene of the 1979 film "The Champ" as a tried-and-true way to turn on the waterworks.

How The Film Was Chosen

When you want to make research subjects feel certain emotions, you have a few options. To make them sad, you can ask them to read depressing statements aloud or listen to emotional music. Ethics, however, keep you from going too much further. You can't lie and tell them a loved one is dead or diagnose them with a fake terminal illness, for example. That's why films work so well: they're designed to elicit emotion, but they rarely cause lasting effects. So in 1988, psychology professor Robert Levenson and his graduate student James Gross set out to identify which movie scenes best brought up a strong emotional response in the lab.

They took 250 suggestions from colleagues and the public, then narrowed those down to 78 individual movie scenes. Next, they played the scenes for nearly 500 undergraduates and surveyed them on the emotions they felt while watching. The researchers were aiming to find scenes that elicited just one emotional response, so they discarded scenes that participants said made them sad and angry, for example, or disgusted and amused. Finally, in 1995, they published their results. When it came to sadness, "The Champ" got a stronger response than any other scene. Even the death of Bambi's mother couldn't hold a candle to it.

Why It's So Sad

If you've never watched "The Champ" (and we don't blame you; it has a 40 percent rating on Rotten Tomatoes) here's the rundown: John Voight plays a gambling, hard-drinking, down-on-his-luck boxer whose ex-wife shows up to claim custody of their adorable son. He realizes that the only way he can keep his son is to return to the boxing ring and mount a glorious comeback. In the end (spoiler alert!) Voight's character wins the big fight, but dies in the dressing room afterward. The final scene (which you can watch here) depicts the inconsolable son weeping and tugging at his dead father, crying "Wake up, Champ!" Misty-eyed yet? We'll give you a second.

Because of its unique ability to make people cry, "The Champ" has been used in thousands of psychology studies — Google Scholar lists more than 4,000. So the next time you hear news about how women's tears reduce testosterone in men or "emotional eaters" eat more when they're sad than when they're happy, you can safely assume which film helped the researchers come to that conclusion.

Bonus fact: The only movie clip that rivaled the emotional response of "The Champ" was in the category of "amusement." That clip? The restaurant scene from "When Harry Met Sally." We'll have what she's having!